1. Field of the Invention
The present invention generally relates to a bicycle front derailleur. More specifically, the present invention relates to a bicycle front derailleur attachable to a bicycle frame that includes a chain guide movable between a retracted position and an extended position.
2. Background Information
Bicycling is becoming an increasingly more popular form of recreation as well as a means of transportation. Moreover, bicycling has become a very popular competitive sport for both amateurs and professionals. Whether the bicycle is used for recreation, transportation or competition, the bicycle industry is constantly improving the various components of the bicycle. One component that has been extensively and continuously redesigned over a long period of time is the front derailleur. Front derailleurs are generally attached to the bicycle frame adjacent to the front chain rings or chain ring set.
In general, front derailleurs are equipped with a fixing member that attaches to the bicycle frame, a linkage mechanism and a chain guide movably coupled to the fixing member by the linkage mechanism, where the linkage mechanism is configured to move the chain guide between an extended position and a retracted position relative to the front chain rings (for example, see to Japanese Laid-Open Patent Application No. 2003-160087).
Conventional linkage mechanisms typically include a first link, a second link, and a third link. The fixing member includes axially aligned and spaced apart first and second attachment flanges. A gap is formed between the first and second attachment flanges. The first link is rotatably coupled to the fixing member at a first rotation point such that rotation of the first link occurs about a first rotational axis. The second link is rotatably supported by the first and second attachment flanges such that rotation occurs about a second rotational axis that is substantially parallel to the first rotational axis. The third link is rotatably coupled to the chain guide and is movably linked to the first and second link to form a four-member linkage mechanism that includes the fixing member. The second link is rotatably supported on to the first and second attachment flanges by a first pivot pin and a second pivot pin that extend into holes in respective ones of the first and second linking flanges. The first and second pivot pins are flanged pins that have a flange or head at one end thereof and are retained in place by a locking ring that is installed at respective distal ends of the first and second pivot pins.
When assembling the linkage mechanism of the front derailleur, the first and second pivot pins are mounted on the first and second attachment flanges from outward sides of the fixing member with the second link disposed adjacent to the first and second attachment flanges. Locking rings are installed on respective distal ends of the first and second pivot pins to retain them in position. When the locking rings are mounted on the distal ends of the first and second pivot pins, the overall number of assembly steps required for the front derailleur is large because both first and second locking pins require a groove to receive the locking rings, and the second link must be held in position as the first and second pivot pins are installed. It is therefore desirable to decrease the number of assembly steps to increase manufacturing productivity.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved front derailleur linkage mechanism design that makes it possible to reduce the number of assembly steps. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.